1. Field Of The Invention
This invention relates to improvements in ink fountains, of the type having a doctor blade, for supplying ink to an ink carrying roll of a printing press, such as an anilox ink transfer roll of a letter press.
2. Description Of The Prior Art
Ink fountain assemblies for supplying ink to the ink transfer roll of a printing press are old and well known. Also, means for controlling or metering the amount of ink carried from the ink fountain by the ink transfer roll, such as doctor blades, are well known and currently in commercial use.
U.S. Pat. No. 4,432,282 to Jurinak, the inventor of the invention disclosed herein, shows a downwardly depending doctor blade positioned between the front and rear walls of an ink fountain. The doctor blade is vertically adjustable with respect to the surface of the ink transfer roll. This disclosure teaches improvements over the invention disclosed in the inventor's previous patent.
U.S. Pat. No. 4,158,333 to Navi shows a baffled ink fountain having the front wall of the ink fountain formed of a reverse angle doctor blade which contacts the surface of a rotating inking cylinder.
U.S. Pat. No. 4,445,433 to Navi shows an ink fountain similar to that shown in U.S. Pat. No. 4,158,333 to Navi. In each of the patents to Navi the doctor blade is shown engaging a portion of the ink transfer surface of an ink transfer roll located in the lower left quadrant of a counterclockwise rotating transfer roll.
Prior art printing presses, such as offset or letter press printing presses, typically required a cumbersome multiplicity of ink working distribution rolls interposed between the ink transfer roll and the printing or plate roll to evenly distribute ink on the plate roll in an effort to reduce, or preferably, eliminate an undesirable uneveness of printing often referred to as "ghosting."
"Ghosting" is caused by having the ink transfer roll acquire a buildup of ink on a particular portion of its surface which corresponds to a portion of the printed material, such as a non-ink receiving white area defined by being surrounded by a red, or other color, ink, placed on the printed material by the print roll. During rotation of the print and ink transfer rolls, and the ink distributing rolls the ink buildup is transferred back onto the print roll and consequently the printed material has a darker red area which is shifted in position but corresponds in size to the non-ink receiving white area.
It is known that the use of a doctor blade optimally adjusted with respect to the ink carrying surface of the ink transfer roll can substantially eliminate such "ghosting." However, the prior art attempts to accomplish this do not provide the degree of adjustment of the doctor blade with respect to the ink transfer roll to substantially eliminate "ghosting" under virtually all conditions. Also, each time a color is changed, or a repair must be made to an ink fountain, the ink fountain must be removed from the press and, upon its reinstallation, a substantial amount of time and testing is required to again adjust the doctor blade into its optimal relationship or engagement with the roll.
Prior art ink fountains also require that a substantial amount of ink be deposited in them in order to properly wet the ink transfer roll. For short runs of the press where a small quantity of the printed material is to be prepared, the ink remaining in the ink fountain will often be wasted due to being disposed of. Such waste of ink imposes an economic penalty on the printer and/or the purchaser of the material.
None of the above cited patents, nor any other prior art of which Applicant is aware, either singly or when combined, teach or show or suggest the ink fountain assembly disclosed below.